A crenellated-target-based calibration method for laser triangulation sensors integration in articulated measurement arms

Point Laser Triangulation (PLT) probes have significant advantages over traditional touch probes. These advantages include throughput and no contact force, which motivate use of PLT probes on Coordinate Measuring Machines (CMMs). This document addresses the problem of extrinsic calibration. We present a precise technique for calibrating a PLT probe to a CMM. This new method uses known information from a localized polyhedron and measurements taken on the polyhedron by the PLT probe to determine the calibration parameters. With increasing interest in applying PLT probes for point measurements in coordinate metrology, such a calibration method is needed. [S1087-1357(00)01703-2]

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A Camera Intrinsic Matrix-Free Calibration Method for Laser Triangulation Sensor

Sensors ◽

10.3390/s21020559 ◽

2021 ◽

Vol 21 (2) ◽

pp. 559

Author(s):

Xuzhan Chen ◽

Youping Chen ◽

Bing Chen ◽

Zhuo He ◽

Yunxiu Ma ◽

...

Keyword(s):

Closed Form Solution ◽

Calibration Method ◽

Industrial Applications ◽

Form Solution ◽

Displacement Measurement ◽

Necessary Condition ◽

Laser Triangulation ◽

Depth Information ◽

One Dimensional ◽

Matrix Free

Laser triangulation sensors (LTS) are widely used to acquire depth information in industrial applications. However, the parameters of the components, e.g., the camera, of the off-the-shelf LTS are typically unknown. This makes it difficult to recalibrate the degenerated LTS devices during regular maintenance operations. In this paper, a novel one-dimensional target-based camera intrinsic matrix-free LTS calibration method is proposed. In contrast to conventional methods that calibrate the LTS based on the precise camera intrinsic matrix, we formulate the LTS calibration as an optimization problem taking all parameters of the LTS into account, simultaneously. In this way, many pairs of the camera intrinsic matrix and the equation of the laser plane can be solved and different pairs of parameters are equivalent for displacement measurement. A closed-form solution of the position of the one-dimensional target is proposed to make the parameters of the LTS optimizable. The results of simulations and experiments show that the proposed method can calibrate the LTS without knowing the camera intrinsic matrix. In addition, the proposed approach significantly improves the displacement measurement precision of the LTS after calibration. In conclusion, the proposed method proved that the precise camera intrinsic matrix is not the necessary condition for LTS displacement measurement.

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STRICT GEOMETRIC CALIBRATION OF AN UNDERWATER LASER TRIANGULATION SYSTEM

ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences ◽

10.5194/isprs-archives-xliii-b2-2021-689-2021 ◽

2021 ◽

Vol XLIII-B2-2021 ◽

pp. 689-692

Author(s):

H. Sardemann ◽

C. Mulsow ◽

H.-G. Maas

Keyword(s):

Laser Light ◽

Light Sheet ◽

Calibration Method ◽

Housing First ◽

Laser Triangulation ◽

Object Surface ◽

Geometric Calibration ◽

Novel Approach ◽

Laser Plane ◽

Underwater Laser

Abstract. This paper will describe a novel approach for the calibration of an underwater laser triangulation system. Underwater triangulation systems, consisting of a line laser and a camera can be used to determine the geometry of submerged objects or the topography of a water body bottom. Placing camera and laser line projector inside a waterproof housing leads to refraction effects at the air-glass-water interfaces, both of the laser light-sheet and image rays. This implies a deformed laser plane in the water and a curved line on the object surface. The proposed approach strictly models the geometry between camera, laser and housing. First experiments show, that the calibration method can be applied for water depth measurements with accuracies of 0.2–0.3 mm at depths in the order of 100 mm.

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A Calibration Method for a Laser Triangulation Scanner Mounted on a Robot Arm for Surface Mapping

Sensors ◽

10.3390/s19081783 ◽

2019 ◽

Vol 19 (8) ◽

pp. 1783 ◽

Cited By ~ 9

Author(s):

Gerardo Antonio Idrobo-Pizo ◽

José Maurício S. T. Motta ◽

Renato Coral Sampaio

Keyword(s):

Turbine Blades ◽

Laser Diodes ◽

Hydraulic Turbine ◽

Calibration Method ◽

Laser Triangulation ◽

Calibration Model ◽

Robot Arm ◽

Surface Mapping ◽

Distance Range ◽

Sensor Position

This paper presents and discusses a method to calibrate a specially built laser triangulation sensor to scan and map the surface of hydraulic turbine blades and to assign 3D coordinates to a dedicated robot to repair, by welding in layers, the damage on blades eroded by cavitation pitting and/or cracks produced by cyclic loading. Due to the large nonlinearities present in a camera and laser diodes, large range distances become difficult to measure with high precision. Aiming to improve the precision and accuracy of the range measurement sensor based on laser triangulation, a calibration model is proposed that involves the parameters of the camera, lens, laser positions, and sensor position on the robot arm related to the robot base to find the best accuracy in the distance range of the application. The developed sensor is composed of a CMOS camera and two laser diodes that project light lines onto the blade surface and needs image processing to find the 3D coordinates. The distances vary from 250 to 650 mm and the accuracy obtained within the distance range is below 1 mm. The calibration process needs a previous camera calibration and special calibration boards to calculate the correct distance between the laser diodes and the camera. The sensor position fixed on the robot arm is found by moving the robot to selected positions. The experimental procedures show the success of the calibration scheme.

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